A semiconductor wafer used to fabricate a semiconductor device is generally manufactured through slicing, grinding, and polishing. That is, a semiconductor ingot that is a material of a semiconductor wafer is sliced by a wire saw or the like to form a thin discoid wafer. In this case, fluctuation occurs in thickness and flatness of a wafer depending on a slicing condition. Moreover, a machining-strain layer in a wafer may increase in size. Therefore, both sides of a wafer cut out from a semiconductor ingot are ground in order to uniform the thickness of the wafer, flatten the wafer, and remove machining-strain layers from the wafer and thereafter, the wafer passes though the polishing and is formed into a product (Japanese Patent Laid-Open Nos. 9-248758, 9-262746, 9-262747, 10-156681, 10-180599, and 10-277898).
The both side grinding of a wafer uses fixed abrasive grains or free abrasive grains. Grinding by fixed abrasive grains grinds a workpiece between so-called grindstones.
Grinding by free abrasive grains grinds a workpiece between rotating surface plates by supplying free abrasive grains between the plates, which is referred to as lapping. It is said that the efficiency of grinding by fixed abrasive grains using a grindstone is exceptionally higher than that of grinding by free abrasive grains.
Grinding by fixed abrasive grains using a grindstone and lapping by free abrasive grains use large diameter abrasive grains because a sliced wafer (wafer to be ground) has a rough surface. In case of grinding by fixed abrasive grains, a holding force for the grindstone tends to increase as the diameter of an abrasive grain increases. Then a surface to be ground is rough, abrasive grains are extremely removed from a grindstone unless the grains have a large diameter and thereby, machining becomes impossible in a short time.